This invention relates to a finishing apparatus including an image forming apparatus such as a copier, a printer, or a facsimile using electrophotography and a finisher for finishing for a record sheet on which an image is already formed from the image forming apparatus and in particular to an improvement in a finisher for performing predetermined punching or stapling for each record sheet.
Hitherto, as this kind of finishing apparatus for performing punching, an apparatus including a punch mechanism (puncher) which previously moves to a predetermined position based on size information of a sheet-like member (record sheet) in a width direction there of and punching information indicating whether or not punching is to be performed wherein the puncher stands by at the position corresponding to a sheet-like member of the maximum width to which punching can be applied when punching is not performed has been proposed, for example, as disclosed in the Unexamined Japanese Patent Application Publication No. Hei 9-249348.
In such a form, an apparatus including a plurality of sheet width direction end face detector placed for performing punching corresponding to a plurality of sheet sizes wherein the sheet width direction end face detector to be used is selected in response to the size information of each record sheet in a width direction thereof for sensing the width direction end face of the record sheet and a move of a puncher is stopped based on the detection information for performing punching under the condition determined for each record sheet is proposed.
In such a form, however, a plurality of detector need to be provided and therefore in addition to an increase in the cost, it becomes difficult to deal with different types of record sheets having close sheet sizes, and it is difficult on design to place a plurality of detector corresponding to the types of record sheets.
A form is also proposed wherein only one sheet width direction end face detector is placed and the time interval between the instant at which the sheet width direction end face detector detects the width direction end face of a record sheet and the instant at which move unit of a puncher is stopped is determined in response to the width direction size information of the record sheet and punching is performed under the condition determined for each record sheet.
According to the form, only one detector is needed and therefore the above-mentioned problem of an increase in the cost is eliminated, but it is necessary to reciprocate the puncher for each record sheet so as to match the size of the record sheet, and a technical problem of incompatibility with a high-speed machine and incapability of realizing high productivity occurs.
Particularly, this technical problem becomes more noticeable as the record sheet size is smaller.
FIGS. 8A and 8B show a comparison between the puncher move distance when the record sheet size is large and that when the record sheet size is small.
As shown in FIG. 8A, if the size of a record sheet S is large, the time interval between the instant at which sheet width direction end face detector 310 detects the width direction end face of the record sheet S and the instant at which move unit of a puncher 300 is stopped is determined and the puncher 300 is moved in the arrow direction in the figure (to the right) for punching at a predetermined position.
At this time, the move distance of the puncher 300 is represented by distance I1 between puncher center A and record sheet center B.
On the other hand, as shown in FIG. 8B, if the size of the record sheet S is small, punching is performed as the size of the record sheet S is large, but the move distance of the puncher 300 is represented by distance I2 and if a comparison is made between I1 and I2, I2 is fairly large as compared with I1, namely, when the size of the record sheet S is small, the puncher 300 must be moved largely.